Keywords

Abstract

In this paper, the three-dimensional ﬁnite diﬀerence in time-domain
method is applied to compute electromagnetic ﬁelds above and
in a uniform or horizontally stratiﬁed ground in the vicinity of a
vertical lightning return-stroke channel. In the computations, the
return-stroke channel is represented with engineering and electromagnetic models. Engineering models used here are the modiﬁed
transmission-line model with linear current decay with height and
the modiﬁed transmission-line model with exponential current decay
with height. Electromagnetic models employed include a vertical
resistive wire having additional series distributed inductance and a
vertical resistive wire coated by a ﬁctitious material having high relative permittivity and permeability. Fields above ground computed
with each lightning return-stroke model are not much inﬂuenced by
the ground stratiﬁcation, but those in the ground are inﬂuenced
more by it. It appears that each model yields reasonably accurate
results of close electromagnetic ﬁelds.